Misfit dislocations in planar, zinc-diffused In 0.53Ga 0.47As PIN photodiodes were analyzed using defect etching, cathode-luminescence, and electron-beam-induced current (EBIC). It was found that the misfit dislocations in wafers grown by liquid-phase epitaxy are present only in the InP buffer layer and they act as non-radiative recombination centers. These dislocations also affect the p-n junction since the misfit stress locally increases the diffusion depth by 80–400 Å. EBIC examination of the photodiodes under reverse bias shows that the misfit dislocations do not cause localized breakdown of the p-n junction.